Many switching technologies rely on solid, mechanical contacts that are alternatively actuated from one position to another to make and break electrical contact. Unfortunately, mechanical switches that rely on solid-to-solid contact are prone to wear and are subject to a condition known as “fretting.” Fretting refers to erosion that occurs at the points of contact on surfaces. Fretting of the contacts is likely to occur under load and in the presence of repeated relative surface motion. Fretting typically manifests as pits or grooves on the contact surfaces and results in the formation of debris that may lead to shorting of the switch or relay.
To reduce mechanical damage imparted to switch and relay contacts, switches and relays may be fabricated using conductive liquid materials to wet the movable mechanical structures to prevent solid to solid contact. A switch that employs a conductive liquid is disclosed in U.S. Pat. No. 6,323,447, entitled “Electrical Contact Breaker Switch, Integrated Electrical Contact Breaker Switch, And Electrical Contact Switching Method.” The switch described in U.S. Pat. No. 6,323,447 uses one or more heaters to heat a non-conducting fluid. The heated non-conducting fluid expands to exert pressure on the conductive liquid. The pressure exerted on the conductive liquid divides the droplet of conductive liquid, thus causing the switching function. Another conductive liquid switch that employs gas pressure to actuate the switch is disclosed in co-pending, commonly assigned, U.S. patent application Ser. No. 11/068,633, entitled “Liquid Metal Switch Employing A Single Volume Of Liquid Metal”. The switch described in U.S. patent application Ser. No. 11/068,633 uses one or more heaters to heat a non-conducting fluid. The heated non-conducting fluid expands to exert pressure on a single volume of conductive liquid. The pressure exerted on the conductive liquid causes the conductive liquid to translate in a cavity, thus causing the switching function.
Unfortunately, due to one or more of contamination, oxidation and amalgamation of the conductive liquid metal, and especially after a period of inactivity, the droplet of conductive liquid tends to adhere to the surfaces of the channel in which it is located and is difficult to move when switching is desired. Prior techniques to minimize the adhesion effect and cause actuation of the conductive liquid droplet include designing the channel in such a way to reduce friction forces between the droplet and the channel, and employing metallic materials for the electrodes that minimize adhesion between the electrodes and the conductive liquid.
However, these techniques have only been marginally successful in minimizing the negative effects on the conductive liquid droplet mentioned above.